59 lines
2.0 KiB
Python
59 lines
2.0 KiB
Python
"""Serve dot diagrams inline.
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SPDX-FileCopyrightText: © 2021 Brian S. Stephan <bss@incorporeal.org>
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SPDX-License-Identifier: AGPL-3.0-or-later
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"""
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import base64
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import logging
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import re
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import markdown
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import pydot
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logger = logging.getLogger(__name__)
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class InlinePydot(markdown.Extension):
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"""Wrap the markdown prepcoressor."""
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def extendMarkdown(self, md):
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"""Add InlinePydotPreprocessor to the Markdown instance."""
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md.preprocessors.register(InlinePydotPreprocessor(md), 'dot_block', 100)
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class InlinePydotPreprocessor(markdown.preprocessors.Preprocessor):
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"""Identify dot codeblocks and run them through pydot."""
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BLOCK_RE = re.compile(r'~~~{\s+pydot:(?P<filename>[^\s]+)\s+}\n(?P<content>.*?)~~~', re.DOTALL)
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def run(self, lines):
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"""Match and generate diagrams from dot code blocks."""
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text = '\n'.join(lines)
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out = text
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for block_match in self.BLOCK_RE.finditer(text):
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filename = block_match.group(1)
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dot_string = block_match.group(2)
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logger.debug("matched markdown block: %s", dot_string)
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logger.debug("match start/end: %s/%s", block_match.start(), block_match.end())
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# use pydot to turn the text into pydot
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graphs = pydot.graph_from_dot_data(dot_string)
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if not graphs:
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logger.debug("some kind of issue with parsed 'dot' %s", dot_string)
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raise ValueError("error parsing dot text!")
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# encode the image and provide as an inline image in markdown
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encoded_image = base64.b64encode(graphs[0].create_png()).decode('ascii')
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data_path = f'data:image/png;base64,{encoded_image}'
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inline_image = f''
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# replace the image in the output markdown
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out = out.replace(block_match.group(0), inline_image)
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return out.split('\n')
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def makeExtension(*args, **kwargs):
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"""Provide the extension to the markdown extension loader."""
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return InlinePydot(*args, **kwargs)
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